摘要:

Six pigeons were trained on three‐alternative concurrent variable‐interval schedules that were available through a switching response and were signaled by colored stimuli. The discriminative stimuli for two of the schedules were always 560 nm and 630 nm, but the stimulus signaling the third alternative was varied across conditions over seven levels between these colors. For each third‐alternative stimulus condition, the relative frequency of reinforcers was varied over three conditions with 4:1 and 16:1 reinforcer ratios between each pair of alternatives. The distribution of responses between the alternatives was dependent jointly on the third‐alternative reinforcer rate and on the disparity between the stimulus signaling the third alternative and those signaling the other alternatives. A generalized matching approach was unable to provide invariant measures of the discriminability between constant stimuli, but a contingency‐discriminability approach provided excellent fits and sensible and invariant stimulus discriminability

ISSN:0022-5002    

DOI:10.1901/jeab.1996.66-149

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Pigeons responded on two keys in each component of a multiple concurrent schedule. In one series of conditions the distribution of reinforcers between keys within one component was varied so as to produce changes in ratios of reinforcer totals for key locations when summed across components. In a second series, reinforcer allocation between components was varied so as to produce changes in ratios of reinforcer totals for components, summed across key locations. In each condition, resistance to change was assessed by presenting response‐independent reinforcers during intercomponent blackouts and (for the first series) by extinction of responding on both keys in both components. Resistance to change for response totals within a component was always greater for the component with the larger total reinforcer rate. However, resistance to change for response totals at a key location was not a positive function of total reinforcement for pecking that key; indeed, relative resistance to extinction for the two locations showed a weak negative relation to ratios of reinforcer totals for key location. These results confirm the determination of resistance to change by stimulus—reinforcer contingenc

ISSN:0022-5002    

DOI:10.1901/jeab.1996.66-169

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Pigeons were trained to peck a key on a variable‐interval 2‐min schedule of food reinforcement. Prior to each session, either 2.0 mg/kg methadone (n= 3), 3.0 mg/kg cocaine (n= 4), or 5.6 mg/kg cocaine (n= 2) was administered. When each pigeon's rate of pecking was stable, a range of doses of the training drug and saline were administered prior to 20‐min extinction sessions separated by at least four training sessions. Rate of pecking during these extinction tests was generally an increasing function of dose, with the lowest rates obtained following saline and low doses and the highest rates obtained following doses near the training doses. Dose functions from pigeons trained with 5.6 mg/kg cocaine were steeper than those from pigeons trained with 3.0 mg/kg cocaine. Pigeons trained with methadone or 3.0 mg/kg cocaine were then given discrimination training, in which food reinforcement followed drug administration and 20‐min extinction sessions followed saline administration. Rates of pecking under these conditions quickly diverged until near‐zero rates were obtained following saline and high rates were obtained following drug. Discrimination training steepened dose functions for the training drugs, and the effects of several other substituted drugs depended on the pharmacology of the training drug. The pigeons trained with 5.6 mg/kg cocaine were tested withd‐amphetamine, methadone, and morphine prior to discrimination training.d‐Amphetamine increased rates dose dependently, and methadone and morphine did not. The results suggest that discriminative control by methadone and cocaine was established without explicit discrimina

ISSN:0022-5002    

DOI:10.1901/jeab.1996.66-193

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Operant responding often changes within sessions, even when factors such as rate of reinforcement remain constant. The present study was designed to determine whether within‐session response patterns are determined by the total number of reinforcers delivered during the session or only by the reinforcers earned by the operant response. Four rats pressed a lever and 3 pigeons pecked a key for food reinforcers delivered by a conjoint variable‐interval variable‐time schedule. The overall rate of reinforcement of the conjoint schedule varied across conditions from 15 to 480 reinforcers per hour. When fewer than 120 reinforcers were delivered per hour, the within‐session patterns of responding on conjoint schedules were similar to those previously observed when subjects received the same total number of reinforcers by responding on simple variable‐interval schedules. Response patterns were less similar to those observed on simple variable‐interval schedules when the overall rate of reinforcement exceeded 120 reinforcers per hour. These results suggest that response‐independent reinforcers can affect the within‐session pattern of responding on a response‐dependent schedule. The results are incompatible with a response‐based explanation of within‐session changes in responding (e.g., fatigue), but are consistent with both reinforcer‐based (e.g., satiation) and stimulus‐based (e.g.,

ISSN:0022-5002    

DOI:10.1901/jeab.1996.66-205

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Rats were exposed to concurrent‐chains schedules in which a single variable‐interval schedule arranged entry into one of two terminal‐link delay periods (fixed‐interval schedules). The shorter delay ended with the delivery of a single food pellet; the longer day ended with a larger number of food pellets (two under some conditions and six under others). In Experiment 1, the terminal‐link delays were selected so that under all conditions the ratio of delays would exactly equal the ratio of the number of pellets. But the absolute duration of the delays differed across conditions. In one condition, for example, rats chose between one pellet delayed 5 s and six pellets delayed 30 s; in another condition rats chose between one pellet delayed 10 s and six pellets delayed 60 s. The generalized matching law predicts indifference between the two alternatives, assuming that the sensitivity parameters for amount and delay of reinforcement are equal. The rats' choices were, in fact, close to indifference except when the choice was between one pellet delayed 5 s and six pellets delayed 30 s. That deviation from indifference suggests that the sensitivities to amount and delay differ from each other depending on the durations of the delays. In Experiment 2, rats chose between one pellet following a 5‐s delay and six pellets following a delay that was systematically increased over sessions to find a point of indifference. Indifference was achieved when the delay to the six pellets was approximately 55 s. These results are consistent with the possibility that the relative sensitivities to amount and delay differ as a function of

ISSN:0022-5002    

DOI:10.1901/jeab.1996.66-219

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Pigeons were studied in two experiments employing delayed matching‐to‐sample (DMTS) tasks in which the reduction in delay to reinforcement signaled by the onset of the sample stimulus was manipulated by varying sample‐stimulus duration. In Experiment 1, the duration of the sample stimulus was either 5 s or 10 s for one sample stimulus and 10 s or 20 s for the other. Subjects matched more frequently when the sample duration was 10 s following the sample associated with the shorter average duration. This finding is analogous to the memory distribution effect found by Honig (1987) in a successive DMTS task that varied retention interval. In Experiment 2, sample duration was either 5 s or 15 s. In Phases 1 and 3 each sample duration was correlated with a particular sample color, and in Phase 2 sample duration and color were uncorrelated. When sample duration was 5 s, subjects matched more frequently when sample duration and color were correlated than when they were uncorrelated. Overall, subjects matched more frequently when sample duration and color were correlated. The data from both experiments support Wixted's (1989) model, which states that one determinant of choice in a DMTS task is the delay‐reduction value of the sample s

ISSN:0022-5002    

DOI:10.1901/jeab.1996.66-231

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

University students participated in one of four standard two‐choice signal‐detection experiments in which signal presentation probability was varied and the reinforcement distribution was held constant and equal. In Experiments 1, 3 and 4, subjects' performance showed a systematic response bias for reporting the stimulus presented least often. Experiments 1 and 4 showed that this effect was reliable with extended training and monetary, rather than point, reinforcement. In Experiment 2, all correct responses were signaled in some way, and this produced the opposite relationship between signal presentation probability and response bias. Experiments 1 and 3 found that explicitly deducting money (intended as punishment) for equal numbers of incorrect responses on each alternative, or varying the obtained overall rate of reinforcement, produced no clear change in response bias. The bias, shown by humans, for reporting the stimulus presented least often remains a challenge for theories of stimulus detect

ISSN:0022-5002    

DOI:10.1901/jeab.1996.66-243

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY